The long term goal of our research is to understand the anatomic and biochemical factors that control aqueous outflow resistance in the normal eye, and the pathophysiologic changes which occur in the glaucomatous eye. Our overall hypothesis is that outflow resistance is caused by the basement membrane of Schlemm 's canal cells, in conjunction with the extracellular matrix (ECM) of the juxtacanalicular region (JCT). The current proposal uses three approaches to investigate this hypothesis: 1) Myocilin: Our results find infusion of myocilin (MYOC, or TIGR) into the human eye increases lOP, probably by specific binding interactions of MYOC within the trabecular meshwork. This enables us to use MYOC as a tool to investigate outflow resistance. We will determine which molecules in the meshwork bind rMYOC, which portion of MYOC is key to this binding, and the ultrastructural location of normal and infused rMYOC in the meshwork. Our perfusion organ culture system for the trabecular meshwork will serve as a "functional assay" for these studies. 2) Laser trabeculoplasty: Our study of glaucomatous human eyes after successful laser trabeculoplasty suggests that laser causes a specific remodeling of the ECM of the JCT. We believe that this is the mechanism of lOP lowering by laser and will test whether it is caused by transient induction of matrix metalloproteases. 3) Disrupt Schlemm's canal cells: If the major site of outflow resistance is in the ECM, disruption of the cells lining Schlemm's canal should cause only a temporary decrease in outflow resistance, despite persistent loss of some cells. Our preliminary studies support this idea, and we will study agents which disrupt the cells lining the canal by different cellular mechanisms to verify this. If the change in resistance is indeed only temporary, this would indicate that the major site of outflow resistance is in the extracellular matrix and not in the cells lining the canal.